JPS61175880A - Broken line extracting device - Google Patents

Abstract

PURPOSE:To extract broken lines at high speed and flexibly even from a picture in which graphic elements such as characters are mixed by binary coding a picture on the two-dimensional plane and inputting, making horizontal and vertical scanning on the input picture, extracting only broken line element constituting a broken line, analyzing their connectivity and recognizing the broken line. CONSTITUTION:Under the control of a controlling section 11, a reading section 12 inputs the graphic elements drawn on a two-dimensional plane as the binary picture of white and black and holds in a processed picture storing section 13. Connecting components in the black picture element area are classified by a line element extracting section 14 into elements of horizontal lines, vertical lines, oblique lines, characters and broken lines, and the data of broken line element are held in a broken line element storing section 15, and the data of the horizontal lines, the vertical lines and the oblique lines are held in a straight line storing section 16. A broken line recognizing section 17 judges the connectivity of data and recognizes the broken lines, and determines the data of broken lines together with the data of the storing section 16 and stores in a broken line storing section 18. At the same time, the broken line is displayed in a display unit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a broken line extraction device that extracts broken lines existing in an image by separating them from other image elements when recognizing or understanding a figure 2 drawing. be.

2. Description of the Related Art In recent years, with the spread of word processors and the like, there has been a tendency to automate tasks such as document creation, and it has become necessary to automatically recognize lines such as solid lines and broken lines for creating tables and the like. A conventional example of the above-mentioned broken line extraction device will be described below with reference to the drawings. Figure 8 shows the configuration of the conventional example;
The figure shows a conventional method for determining the connectivity of broken line elements that are constituent elements of broken lines. In Figure 8, 1 is the image 2
2 is an image reading unit that converts the value into a value and inputs the data; 2 is a thinning unit that represents a simply connected black pixel area with a bone-like line with a width of 1 pixel; 3
4 is a bending point extraction unit that extracts a bending point where the angle suddenly changes within one thinned area, 4 is a direction determination unit that determines the directionality of each thinned element, and 5 is an element to be connected. This is a connectivity determination unit that determines. Also, in Figure 2, a
, b represent the thinned elements, al , a2 . b
l.

b2 represents both end points of a and b, and θ represents the angle formed by a and b. The operation of the broken line extraction device configured as shown in FIG. 8 will be described below.

First, an image reading section 1 binarizes a target image and inputs it into an image memory. Next, in the thinning section 2, all singly connected black pixel areas of the input image are thinned. At this time, for the thinned element whose length is less than a certain threshold, the point where the angle suddenly changes is detected by the bending point extraction part 3 below, and both end points, branching points, and the above bending point are newly added. Divide the element into multiple parts if necessary so that the endpoints are correct.

The direction determining section 4 determines the direction of the element from the coordinates of both end points of the element. Finally, in the connectivity determining section 5, connectivity of each element is determined. In the case of the a and b2 elements shown in FIG. 9, the above connectivity determination is performed if one end point b1 of b exists within a certain threshold distance from a2, which is one end point of a,
It is assumed that connection is possible when the angle θ formed by a and b (that is, the absolute value of the difference between the direction of a and the direction of b) is within a certain threshold. In this way, each element is connected, and the connected portion is extracted as a broken line.

Problems to be Solved by the Invention However, with the above configuration, a lot of processing time is required due to complicated processing such as thinning or determining the direction of elements, and graphical elements such as characters are mixed on the image. In some cases, not only is there unnecessary processing, but the above graphical elements are mistakenly included as part of the dashed line, and furthermore, because a fixed distance threshold is used to determine the connectivity of the dashed line elements, the length of the dashed line element is When there is a change in the distance between the dashed lines and the intervals between them, there is a problem that the dashed line elements cannot be connected well and the dashed line cannot be extracted as intended. In view of the above problems, the present invention has been developed to In addition to other line elements such as curves, graphic elements such as characters may be mixed, and the present invention provides a broken line extraction device that can flexibly respond to changes in the length and interval of broken line elements.

Means for Solving the Problems In order to solve the above problems, the broken line extraction device of the present invention has a reading section that binarizes and inputs an image expressed on a two-dimensional plane, and a reading section that binarizes and inputs an image expressed on a two-dimensional plane. and a line element extraction unit that scans in the vertical direction and classifies the connected components of black pixels into horizontal lines, vertical lines, diagonal characters, and dashed line elements that are constituent elements of broken lines, and analyzes the connectivity of the dashed line elements. The present invention includes a broken line recognition unit that recognizes broken lines.

Operation The present invention uses the above-mentioned configuration to extract only broken line elements that are constituent elements of a broken line from an input image containing characters, etc. in addition to other line elements such as straight lines and curves, and extracts only broken line elements that are constituent elements of broken lines. By appropriately determining connectivity, it is possible to perform fast and flexible dashed line extraction.

EXAMPLE Hereinafter, an example of the broken line extracting device of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a broken line extraction device in an embodiment of the present invention. In FIG. 1, a control unit 11 controls the execution procedure and data flow of the entire broken line extraction device. 1
Reference numeral 2 denotes a reading unit which inputs graphic elements drawn on a two-dimensional plane such as paper as a black and white binary image. Reference numeral 13 denotes a processed image storage unit that stores the input image as binary data. 14
The line element extraction unit classifies the connected components of the black pixel area into horizontal lines, vertical lines, two characters with diagonal lines, and broken line elements that are constituent elements of broken lines. Reference numeral 16 denotes a broken line element storage unit, which holds data of broken line elements. Reference numeral 16 denotes a linear storage unit that holds data for horizontal lines, vertical lines, and diagonal lines. 17 is a broken line recognition unit that determines the connectivity of the data in 16, recognizes the broken line, and determines the broken line data together with the data in 16. 18 is a broken line storage unit that holds broken line data. A display section 19 displays a broken line based on the data 18.

The broken line extraction device configured as described above is shown in FIGS. 1, 2, 3, 4, and 6 below.

The operation will be explained using FIGS. 6 and 7.

The binary image inputted by the reading section in FIG. 3 and 12 is held in the processed image storage section 13. This image is first scanned once in the horizontal and vertical directions in the 14 line element extraction units, and consecutive parts of black pixels in the horizontal and vertical directions with lengths longer than a certain threshold are extracted as horizontal lines and vertical lines, respectively. Detected. After this, perform another horizontal scan to find the horizon line.

Connected areas of black pixels other than vertical lines are classified into two diagonal line characters and broken line elements. Here, diagonal lines can be easily distinguished because they have a monotonous upward or downward slope to the right and occupy a larger area than characters, so it becomes a problem to distinguish between characters and broken line elements. Therefore, for each connected black area other than horizontal lines, vertical lines, and diagonal lines, it is determined whether it is a character or a broken line element, and those classified as broken line elements are stored as data in the 15 broken line element storage units. . Figure 4 shows the classification of characters and dashed line elements.As shown in Figure 4a, there are those with loops in the connected black pixel area, and those with deep loops on one or more of the four sides of the top, bottom, left, and right. Those with concavities (above a threshold value) are classified as characters, and those with the shape shown in Figure 4 are classified as broken line elements. In this example, since broken lines are limited to those in the horizontal and vertical directions, the shape of the circumscribed rectangular frame of the broken line element allows the broken line element to be defined as a horizontal broken line (hereinafter referred to as horizontal broken line). vertical broken line elements, which are components of vertical broken lines (hereinafter referred to as vertical broken lines), and connected broken line elements that occur at the intersections of horizontal broken lines and vertical broken lines. If a dashed line in a diagonal direction is considered, it may be determined whether it is monotonous upward to the right or downward to the right and classified into dashed line elements in that direction. Further, data of horizontal lines, vertical lines, and diagonal lines are held in the linear storage section of FIG. 316.

The data of horizontal lines, vertical lines, diagonal lines, and each broken line element extracted by the line element extraction section is code information listed so that there is no need to access pixel data on a two-dimensional plane thereafter. FIG. 5a shows an example of the contents of the horizontal broken line element data.

The broken line recognition unit shown in FIG. 317 recognizes broken lines by determining the connectivity between each broken line element from the data of the broken line elements. Horizontal broken lines and vertical broken lines are recognized using the same method, so the horizontal broken lines will be explained as an example. All horizontal dashed line elements are sorted in ascending order of their vertical coordinate values (hereinafter referred to as y coordinates), so that two adjacent dashed line elements whose y coordinate value difference is less than a threshold constitute one cluster. Clustering. FIG. 6 shows the above clustering.

In this case, all horizontal dashed line elements can be classified into three clusters, a, b, and c. Next, the horizontal dashed line elements in the same cluster are sorted in ascending order of the horizontal coordinate value (hereinafter referred to as I coordinate)', the connectivity between two adjacent dashed line elements is determined, and the connectable parts are combined into one broken line. recognized as In the case of Figure 6, al
, a2. Four broken lines b and c can be recognized.

The connectivity in the horizontal direction is such that the difference in the y-coordinates of two adjacent horizontal dashed line elements is equal to or less than a threshold value, and the distance between two adjacent horizontal dashed line elements in the horizontal direction and the total length including the interval as shown in FIG. It is assumed that connection is possible when the white ratio W, which is the ratio of In FIG. 6, m and n are both horizontal dashed line elements; 2. is the horizontal length of the space between m and n, and 2a is the sum of the horizontal lengths of m and n. is added. Broken line data is also held as listed code information. FIG. 5 shows the contents of horizontal broken line data as an example.

After vertical broken lines are also recognized in the same manner as above, the broken lines are integrated using connected broken line elements. Figure 8 shows the situation. Since a connected dashed line element occurs at the intersection of a horizontal broken line and a vertical broken line, integration is performed only when there is at least one horizontal broken line and one vertical broken line on both the top, bottom, left, and right sides of the connected dashed line element within the range that can be connected with the white ratio. .

Even after the integration is complete, it is determined that a dashed line that has very few component dashed line primes is actually a character with a simple shape extracted as a dashed line element, and is removed as not being a broken line.

Finally, determine the end points of the broken line, that is, the start and end points.

In principle, the end points of a broken line and the end points of both ends of the broken line elements that make up the broken line should be two end points that have no connected broken line elements nearby, but in the case shown in Figure 9, the two end points of j and ni. Since it is reasonable for both dashed lines to start from the vertical line p, it is also possible to move the end points of the dashed lines above p. If there is no solid line or broken line perpendicular to the vicinity of the end point, there is no need to move the end point.

The dashed line data recognized as busy as above is 18 in Figure 3.
It is held in the dashed line storage section. If necessary, it can be displayed on 19 display sections.

Effects of the Invention As described above, the present invention includes a reading unit that binarizes and inputs an image expressed on a two-dimensional plane, and scans the input image in the horizontal and vertical directions to convert connected components of black pixels into horizontal lines. , by providing a line element extraction unit that classifies vertical lines, diagonal lines, two characters, and dashed lines into broken line elements that are constituent elements, and a broken line recognition unit that analyzes the connectivity of broken line elements and recognizes broken lines. Broken lines can be extracted quickly and flexibly from images containing not only other line elements such as characters, but also graphic elements such as characters.

[Brief explanation of drawings]

FIGS. 1 to 7 relate to the present invention. FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing discrimination between characters and broken line elements, and FIG. 3 is a diagram showing horizontal broken line elements. Figure 4 is a diagram showing clustering of horizontal dashed line elements, Figure 5 is a diagram of white percentage for determining connectivity of dashed line elements, and Figure 6 is a diagram of dashed lines using connected dashed line elements. 7 is a diagram showing how end points of broken lines are determined, FIG. 8 is a block diagram of a conventional broken line extraction device, and FIG. 9 is an explanatory diagram of the operation of the same device. 11...Control unit, 12...Reading unit, 1
3... Processed image storage section, 14... Line element extraction section, 16... Broken line unstored section, 16...
...Line storage section, 17...Dotted line recognition section, 1
8... Broken line storage section, 19... Display section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure/'/ Data θ Wrapped in One ---- Control Board Figure 2 Letters/+Ita 14 Figure 3 (C1) Figure 4 One Sea Between Figure 5 Yv211/j! ^ Figure 6 Figure 7

Claims (1)

[Claims] A reading unit that binarizes and inputs an image expressed on a two-dimensional plane, and a reading unit that scans the input image in the horizontal and vertical directions and converts connected components of black pixels into horizontal lines, vertical lines, diagonal lines, characters, and broken lines. What is claimed is: 1. A broken line extraction device comprising: a line element extraction unit that classifies broken line elements as constituent elements; and a broken line recognition unit that analyzes connectivity of the broken line elements and recognizes the broken line.